ИСТИНА

Rheological analyses of soil structure allows studying the mechanical behavior of soils under load, which gives us a quantitative description of the inter-particle interactions and fundamental information of the structural deformation of soils. Markgraf et al. (2006) showed that micro-structural stability is influenced by clay mineralogy, texture and organic matter, which lead to different shear behavior. A key soil parameter which influence on soil stability is soil organic carbon (SOC) and its composition (Tisdall and Oades, 1982; Shein and Milanovsky,2003). In this work we investigated shear behavior of soils with the high and low content of organic matter. The top layer 0-10 cm of silty clay typical chernozems from native steppe and bare fallow soil of State Central Chernozem Reserve (Streletzkaya Steppe, Kursk, Russia) were used. Highest concentration of soil organic carbon (SOC) was detected in native steppe (6.1%) and the lowest - in bare fallow (3.1%). Amplitude sweep tests (AST) were conducted with modular compact rheometer MCR 302 (Anton Paar, Germany) with parallel plates measuring system. The chernozem of the virgin steppe of State Central Chernozem Reserve with the larger contents organic substance (6,1%) showed high degree of a micro-structural stability, and the chernozem being under the long-term bare fallow with the content of organic matter of 3.5% showed considerably smaller degree of a micro-structural stability that confirms the thesis (Tisdall and Oades, 1982; Shein and Milanovsky, 2003) about a predominating role of organic matter in the organization of steady structure. This research showed that rheological methods and the received parameters, such as elastic modulus, viscous modulus and an integral zone z are the useful, highly sensitive tools for the description and the quantitative assessment of a micro-structural stability of studied objects.